全文获取类型
收费全文 | 9571篇 |
免费 | 967篇 |
国内免费 | 1686篇 |
出版年
2024年 | 16篇 |
2023年 | 304篇 |
2022年 | 294篇 |
2021年 | 398篇 |
2020年 | 437篇 |
2019年 | 494篇 |
2018年 | 422篇 |
2017年 | 412篇 |
2016年 | 427篇 |
2015年 | 443篇 |
2014年 | 495篇 |
2013年 | 753篇 |
2012年 | 408篇 |
2011年 | 470篇 |
2010年 | 391篇 |
2009年 | 542篇 |
2008年 | 551篇 |
2007年 | 566篇 |
2006年 | 536篇 |
2005年 | 415篇 |
2004年 | 373篇 |
2003年 | 377篇 |
2002年 | 271篇 |
2001年 | 248篇 |
2000年 | 240篇 |
1999年 | 183篇 |
1998年 | 175篇 |
1997年 | 187篇 |
1996年 | 146篇 |
1995年 | 136篇 |
1994年 | 138篇 |
1993年 | 130篇 |
1992年 | 130篇 |
1991年 | 99篇 |
1990年 | 93篇 |
1989年 | 77篇 |
1988年 | 68篇 |
1987年 | 52篇 |
1986年 | 61篇 |
1985年 | 70篇 |
1984年 | 38篇 |
1983年 | 25篇 |
1982年 | 38篇 |
1981年 | 33篇 |
1980年 | 14篇 |
1979年 | 15篇 |
1978年 | 8篇 |
1977年 | 8篇 |
1973年 | 4篇 |
1972年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
1.
Shunsuke Yaguchi Atsuko Yamazaki Wakana Wada Yasutaka Tsuchiya Toshihiko Sato Hideo Shinagawa Yutaro Yamada Junko Yaguchi 《Development, growth & differentiation》2015,57(3):242-250
Sea urchins are model non‐chordate deuterostomes, and studying the nervous system of their embryos can aid in the understanding of the universal mechanisms of neurogenesis. However, despite the long history of sea urchin embryology research, the molecular mechanisms of their neurogenesis have not been well investigated, in part because neurons appear relatively late during embryogenesis. In this study, we used the species Temnopleurus reevesii as a new sea urchin model and investigated the detail of its development and neurogenesis during early embryogenesis. We found that the embryos of T. reevesii were tolerant of high temperatures and could be cultured successfully at 15–30°C during early embryogenesis. At 30°C, the embryos developed rapidly enough that the neurons appeared at just after 24 h. This is faster than the development of other model urchins, such as Hemicentrotus pulcherrimus or Strongylocentrotus purpuratus. In addition, the body of the embryo was highly transparent, allowing the details of the neural network to be easily captured by ordinary epifluorescent and confocal microscopy without any additional treatments. Because of its rapid development and high transparency during embryogenesis, T. reevesii may be a suitable sea urchin model for studying neurogenesis. Moreover, the males and females are easily distinguishable, and the style of early cleavages is intriguingly unusual, suggesting that this sea urchin might be a good candidate for addressing not only neurology but also cell and developmental biology. 相似文献
2.
《Bioorganic & medicinal chemistry letters》2014,24(3):949-953
We designed and synthesized a novel series of phenylamino- and phenoxy-substituted pyrazolo[3,4-d]pyrimidine derivatives as GPR119 agonists. SAR studies indicated that electron-withdrawing substituents on the phenyl ring are important for potency and full efficacy. Compound 26 combined good potency with a promising pharmacokinetic profile in mice, and lowered the glucose excursion in mice in an oral glucose-tolerance test. 相似文献
3.
Luis Santamaría Jesús Balsa Beatriz Bidondo Angel Baltanás Carlos Montes 《Hydrobiologia》1992,246(2):89-98
Laboratory experiments and field data were used to determine salinity tolerance limits of three ostracode species (Prionocypris aragonica, Eucypris mareotica and Heterocypris barbara) from Iberian saline lakes. Salinity tolerance appeared related to ionic composition and temperature. Implications for ostracode ecology and geographical distribution are evaluated. 相似文献
4.
Protected cultivation of ornamental flowers, as a commercial venture, becomes less profitable with excessive use of fertilizers. The present study examined the influence of microbial biofilm inoculants (Anabaena–Azotobacter, Anabaena–Trichoderma and Trichoderma–Azotobacter) on the availability of soil nutrients and structure of rhizosphere microbial communities in three varieties of chrysanthemum (var. White Star, Thai Chen Queen and Zembla). Varietal-specific responses in growth, enzyme activities, flower yield of plants and availability of soil nutrients were recorded. Dehydrogenase activity was highest in var. White Star treated with the Anabaena–Trichoderma biofilm inoculants. The Anabaena–Azotobacter inoculant enhanced the availability of nitrogen, phosphorus and micronutrients in the soil, besides 40–50% increase in soil organic carbon, as compared to carrier alone or no inoculation. PCR-DGGE profiling of the cyanobacterial communities and qPCR quantification of 16S rRNA abundance of bacteria, archaea and cyanobacteria in the rhizosphere soils, revealed the stronger influences of these inoculants, especially in var. Zembla. Principal Component Analysis (PCA) helped to illustrate that the enhanced microbe-mediated availability of soil macro-and micronutrients, except iron content (Fe), was the most influential factor facilitating improved plant growth and yield parameters. The Anabaena–Azotobacter, and Anabaena–Trichoderma biofilm inoculants, proved superior in all three chrysanthemum varieties. 相似文献
5.
6.
Larvae of the scarabaeid, Cyclocephala hirta, are major pests of turfgrass in California. A field test was conducted against third instars that included the following treatments: untreated control; chemical insecticide (bendiocarb); milky disease bacterium (Bacillus popilliae); and entomopathogenic nematodes (Steinernema feltiae and Heterorhabditis bacteriophora). There were no significant differences in population reduction among the treatments, but the larval population in all plots showed a dramatic decline. The C. hirta population had a natural occurrence of milky disease and blue disease caused by Rickettsiella popilliae. The prevalence of blue disease during the course of the study averaged < 10% but that of milky disease averaged about 20%. More significantly, the soil from all treatment plots when bioassayed for B. popilliae showed that 67–90% of the larvae became infected with this bacterium. None of the larvae became infected with the blue disease organism. We conclude that B. popilliae was occurring in epizootic proportions in our field tests and was a significant mortality factor in causing the decline of the C. hirta population. 相似文献
7.
8.
Genetically modified cells of Pseudomonas fluorescens, chromosomally marked with genes for bioluminescence, were inoculated into sterile soil microcosms. During incubation for 90 days, viable cell concentration did not change significantly but light output, measured by luminometry, decreased, indicating reduced metabolic activity due to lack of substrates. Amendment with nutrients resulted in parallel increases in both luminescence and dehydrogenase activity. Luminometry therefore enables rapid monitoring of the activity of populations of luminescence-marked microbial inocula in the soil, with greater sensitivity and selectivity than traditional techniques. 相似文献
9.
10.